Herendeen D R, Kassavetis G A, Barry J, Alberts B M, Geiduschek E P
Department of Biology, Center for Molecular Genetics, University of California, San Diego, La Jolla 92093.
Science. 1989 Sep 1;245(4921):952-8. doi: 10.1126/science.2672335.
The expression of the late genes in bacteriophage T4 development is closely connected to viral DNA replication. Three T4-encoded DNA polymerase accessory proteins are shown to stimulate transcription at T4 late promoters in an adenosine triphosphate (ATP) hydrolysis-requiring process. The properties of the activation resemble those found for enhancers of eukaryotic transcription. However, the nature of the enhancer of T4 late transcription is novel in that it is a structure--a break in the nontranscribed DNA stand--to which the three replication proteins bind, rather than a sequence. Since the three DNA polymerase accessory proteins are carried on the moving replication fork as part of the replisome, we postulate that viral DNA replication forks act, in vivo, as the mobile enhancers of T4 late gene transcription. Whereas Escherichia coli RNA polymerase bearing the T4 gene 55 protein can selectively recognize T4 late promoters, it is only capable of responding to the transcription-enhancing activity of the three replication proteins on acquiring an additional T4-specific modification.
噬菌体T4发育过程中晚期基因的表达与病毒DNA复制密切相关。三种由T4编码的DNA聚合酶辅助蛋白被证明在一个需要三磷酸腺苷（ATP）水解的过程中刺激T4晚期启动子处的转录。这种激活特性类似于真核转录增强子的特性。然而，T4晚期转录增强子的性质是新颖的，因为它是一种结构——非转录DNA链中的一个断裂——三种复制蛋白结合于此，而不是一个序列。由于这三种DNA聚合酶辅助蛋白作为复制体的一部分位于移动的复制叉上，我们推测病毒DNA复制叉在体内作为T4晚期基因转录的移动增强子。虽然携带T4基因55蛋白的大肠杆菌RNA聚合酶能够选择性识别T4晚期启动子，但只有在获得额外的T4特异性修饰后，它才能够对三种复制蛋白的转录增强活性作出反应。
